The present invention relates to a control of a flow-through valve in general, and more particularly to a control of a valve to be used in a motor vehicle for regulating a climate-controlling arrangement thereof.
Flow-control valves, even pneumatically operated ones, are already known in a variety of constructions and used in a multitude of applications. A pneumatically operated valve usually includes a control side which controls the flow of a medium through a conduit, and an actuating side to which a pneumatic fluid is admitted to act on the valve for moving the same at least between the open and the closed position thereof. For the operation of the valve only between the open and closed positions, it is already known to utilize the pressure differential between the pressure generated by a source which is in communication with the actuating side of the flow-control valve, and the ambient pressure.
In this context it has also been already proposed to utilize the subatmospheric pressure which develops in the intake manifold of the internal combustion engine of the vehicle for operating the flow-control valve of the climate-controlling arrangement of the vehicle. Under these circumstances, the subatmospheric pressure which exists at the actuating side of the flow-control valve due to the communication thereof with the intake manifold of the engine, displaces the valve member of the flow-control valve into its open position provided that the differential between the subatmospheric pressure and the ambient pressure is sufficiently great, while the flow-through valve remains closed when such pressure differential is small or non-existent.
Experience with the pneumatically operated flow-through valves of this type as used for regulating the flow of a heat-exchange medium through a circuit of an arrangement for controlling the climate inside a motor vehicle has shown that, generally speaking, these valves function to satisfaction. However, it has also been established that, under certain circumstances, the pneumatic operation of the valve may malfunction so that the entire climate-controlling arrangement becomes inoperative. There are several reasons why the actuating side of the flow-through valve may cease to operate. So, for instance, the conduit communicating the actuating side of the flow-through valve with the intake manifold of the engine may become obstructed so that the actuating pressure at the actuating side of the flow-through valve will be the same as the ambient pressure. On the other hand, a leak may develop at the actuating side of the flow-control valve so that, despite the communication of the actuating side with the intake manifold, no subatmospheric pressure will develop at the actuating side of the flow-control valve. Also, in a flow-control valve of the type having a switching element which admits either the subatmospheric pressure or the ambient pressure to the actuating side of the flow-control valve, which switching element is operated by an electromagnet, any malfunction in the operation of the electromagnet which causes the actuating side of the flow control valve to permanently communicate with the ambient atmosphere will result in a malfunction of the entire heat-exchange arrangement controlled by the flow-control valve.